#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 
# Copyright (c) 2017 Baidu.com, Inc. All Rights Reserved
# 

"""
File: run1.py
Author: zhangyang(zhangyang40@baidu.com)
Date: 2018/1/5 0005 9:43
"""
"""
题目描述
输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。
假设输入的前序遍历和中序遍历的结果中都不含重复的数字。
例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，
则重建二叉树并返回。
"""


class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None


class Solution:
    # 返回构造的TreeNode根节点
    def reConstructBinaryTree(self, pre, tin):
        map = dict()
        for i in range(0, len(tin)):
            map[tin[i]] = i
        return self.preIn(pre, 0, len(pre) - 1, tin, 0, len(tin) - 1, map)

    def preIn(self, p, pi, pj, n, ni, nj, map):
        if pi > pj:
            return None
        head = TreeNode(p[pi])
        index = map[p[pi]]
        head.left = self.preIn(p, pi + 1, pi + index - ni, n, ni, index - 1, map)
        head.right = self.preIn(p, pi + index - ni + 1, pj, n, index + 1, nj, map)
        return head


if __name__ == '__main__':
    s = Solution()
    tree = s.reConstructBinaryTree([1, 2, 4, 7, 3, 5, 6, 8], [4, 7, 2, 1, 5, 3, 8, 6])
